Three general approaches have been used in recent times for drug development (1) screening large numbers of synthetic test compounds of diverse chemical structure (2) mimicking nature by designing compounds that exert an effect similar to a naturally occurring substance and (3) modifying the structure of an already known drug to maximize or improve one property or minimize an undesirable property. Classically, however, isolation of active principles from biological materials has been quite successful in producing therapeutically useful substances. The isolation of insulin from pancreas glands, quinine from Cinchona bark, and within the field of immunology, the isolation of polypeptide-like materials (Thymosin V, Thymopoietin) derived from the thymus gland which are able to restore or augment depressed immunity are a few examples. A method for restoration of depressed immunity can be medically useful in any disease in which a primary immunodeficiency exists or a secondary immunodeficiency is produced.
The discovery of hormones derived from the thymus and their use in medicine has recently become important and there is considerable literature thereon, for example:
Goldstein U.S. Pat. No. 4,002,740 PA1 Goldstein U.S. Pat. No. 4,079,127 PA1 DeSomer U.S. Pat. No. 3,438,859 PA1 Goldstein U.S. Pat. No. 4,082,737 PA1 Yeshiva British Pat. No. 1,195,980 PA1 Brunetti U.S. Pat. No. 3,657,417 PA1 Goldstein U.S. Pat. No. 4,002,602 PA1 Goldstein U.S. Pat. No. 4,077,949 PA1 Renoux, The Journal of Experimental Medicine, Vol. 145 (1977)pages 466-471
The entire disclosure of the above U.S. patents, British patent and Renoux article are hereby incorporated by reference and relied upon.